“Natural” Eye Drops
Let’s talk about eye drop ingredients and the word “natural”
PART 1: What do you mean by “natural”?
Many eye drop ingredients do not exist in nature, but start from substances that are found in nature. It is simply a question of how much effort has gone into chemically altering those substances to make them suitable and effective in eye drops.
In some cases, a natural ingredient may be cleaned of impurities but otherwise used unaltered (sodium chloride, water). In other cases, a substance may undergo very extensive alteration through heat, chemical reactions, pressure, fermentation, filtration and other methods before it becomes a useful eye drop ingredient (e.g. most glycerin is a byproduct of biodiesel production; polyethylene glycol begins with ethylene produced from natural gas).
Some ingredients do not start from natural substances and are instead produced entirely at chemical manufacturing facilities. The processes used to make these ingredients may be simpler and less “unnatural” than those used to turn a natural substance into an eye drop ingredient. Unlike ingredients created from natural substances, these chemicals often require little additional purification.
Many patients who want more “natural” eye drops really mean they want eye drops with fewer ingredients, or fewer highly processed ingredients, or fewer ingredients with frightening chemical names. However, understanding what is and is not a highly processed ingredient is a complex task, and involves individual value judgements about what types of transformation a patient would consider “more” or “less” natural.
PART 2: Why are there so many ingredients in this eye drop?
The FDA legally divides all ingredients into Active and Inactive Ingredients.
All artificial tears must list at least one allowed lubricant as an Active Ingredient, and this ingredient must always be present in the concentration specified.
Additional lubricants may be listed under Inactive Ingredients, without a concentration. The decision to list a second or third lubricant as Inactive rather than Active is up to the manufacturer and may be made, in part, to conceal the concentration of the additional lubricant(s) from competitors. For OTC products, manufacturers do not provide the concentrations of Inactive Ingredients to the FDA.
Eye drops also contain a number of small, simple molecules that perform important jobs such as adjusting pH to neutral (hydrochloric acid, sodium hydroxide); maintaining pH (buffers); and mimicking the composition of natural tears (salts). These small molecules make eye drops safer, not less safe. The manufacturing processes for these ingredients are simple and they are typically found in numerous products we use daily, including many foods.
Slightly larger molecules are used for adjusting thickness (viscosity agents) and keeping ingredients blended (emulsifiers). The thickeners and emulsifiers may be minimally altered from a natural substance (e.g. dextrose) or moderately altered. One ingredient may be both a thickener and an emulsifier.
Eye drops in standard eye drop bottles also must contain one or more preservatives to decrease the risk of bacterial contamination of the bottle contents during use. Preservatives are listed under Inactive Ingredients but are only rarely identified as preservatives, something we consider to be a problem for consumers.
A final type of Inactive Ingredient might be described as “almost certainly harmless but probably useless.” These include amino acids and vitamins. Although these molecules may be found in natural human tears, there is no indication that they make an artificial tear more effective. In addition, the concentration of these ingredients may be almost vanishingly small, but neither the FDA nor the consumer knows this.
PART 3: If Your Definition of More Natural Means…
More Natural = Less Harmful?
Some artificial tears do contain ingredients which are undesirable. These ingredients are unfortunately prevalent because they have been used for decades and are inexpensive. Avoiding them is a simple way to make a smart choice about your eye drops.
The most obvious type of ingredient to eliminate is preservatives. Preservative-free eye drops are available either in single-use vials or in multi-dose preservative free bottles. Many long-established drops are now available in MDPF bottles. Thicker products cannot pass through the “one way” membranes or filters in MDPF bottles and are available preservative-free only in vials.
More Natural = Fewer Ingredients?
First, there is no reason to avoid salts (ingredients which end in ‘chloride’). Sodium chloride, magnesium chloride, potassium chloride and calcium chloride are all normally found in human tears. However, if you want a shorter list, the magnesium, potassium and calcium salts are not contributing to the lubricating effect of the drop so look for a product without them. Sodium chloride is the ingredient which – combined with water – makes up normal saline.
Second, look for a product that does not include amino acids, vitamins or other “nutritional” ingredients. These are not contributing to your symptom relief. Strenuously avoid products that make drug claims such as decreasing your chance of developing cataracts; these products typically contain amino acids or other small molecules that have zero proven effect.
Third, look for a product that does not have a thickener or an emulsifier. You may be limiting yourself at this point. Many thickeners and emulsifiers are derived from natural substances such as plant sugars (e.g. dextrose comes from corn starch) or guar gum. The chemical reactions that are used to convert the natural substances into a thickener or emulsifier are often rather low-key.
Fourth, do NOT avoid products with hydrochloric acid, sodium hydroxide, or buffers (examples of buffers are listed below). These are essential to maintain the proper pH. The buffers are found in numerous other products including foods. Unbuffered products may have a correct pH when first opened but then drift up or down over time as room air is introduced into the bottle during use. If you use a product that feels great when first opened, but stings when the bottle has been in use for more than 30 days, it is possible that the pH is drifting.
More Natural = Fewer Chemical Sounding Names?
What’s in a name?
Glycerin is a very safe-sounding ingredient and is one of the oldest eye drop lubricants. It has been used medicinally for over 100 years. Adults of a certain age will remember the dreaded glycerin suppository in childhood.
Glycerin can be purified to various degrees, with pharmaceutical grade glycerin being pure glycerin. One type of pharmaceutical grade glycerin is not better than the other: it is all pure glycerin. There are several lower grades of glycerin, such as food grade glycerin (99.7% pure).
Nobody makes glycerin on purpose, it is always the waste product of a more lucrative business. About 70% of glycerin is generated as a by-product of biodiesel manufacturing, which starts with plant or animal oils (including waste oils). These oils undergo numerous industrial processes before producing biodiesel and crude glycerin.
Carboxymethylcellulose start with cellulose (e.g. cotton) which also undergoes a several-step chemical process which results in a purified powder that dissolves readily in water.
Glycerin may sound simpler and less ‘chemical’ than carboxymethylcellulose, but there is no rational reason to prefer one over the other in your eye drop. Both are manufactured via industrial-scale processes that require several steps, including mixing with other chemicals or gasses.
More Natural = Organic?
A 100% organic eye drop doesn’t have many ingredient options. In fact, buying such an eye drop from a legitimate manufacturer is one good way to get a very short ingredient list: the organic lubricant, sodium chloride and water.
Eye drops with lubricants or other ingredients derived from plants can describe themselves as organic if the plants are grown under organic conditions and the production processes for all the ingredients meet the definition for ‘organic handling’. One example is glycerin, which is a common food ingredient that acts as a thickener and adds sweetness. The organic foods industry has been a driver of organic glycerin production.
Organic handling includes techniques such as hydrolysis (treatment with very high temperature and pressure), saponification (treatment with lye) and fermentation (digestion by microorganisms). Crude glycerin produced from plants then has to undergo purification. You may or may not consider glycerin produced on an industrial scale by these methods to fulfill your concept of an ‘organic’ eye drop ingredient.
As a consumer you might prefer to support organic farming practices, and the idea of an eye drop that started as used French fry oil may be repellant. However, from a health perspective, there is no chemical difference between ordinary pharmaceutical grade glycerin and organic pharmaceutical grade glycerin.
If you are minimizing your use of an ‘organic’ eye drop due to cost, and you would use the non-organic equivalent more frequently, you are doing yourself a disservice.
Interesting historical fact: 107 deaths – many of them children – due to an elixir compounded with contaminated glycerin spurred the creation of the Federal Food, Drug and Cosmetic Act. The Act originally required only evidence of safety, not of efficacy.
https://www.ams.usda.gov/sites/default/files/media/Glycerin%20Petition%20to%20remove%20TR%202013.pdf
